Protein interactions in reduced-fat and full-fat Cheddar cheeses during melting

Changes in physicochemical properties of 12-wk-old, half-fat (50 g/100 g reduced-fat) and full-fat Cheddar cheeses on heating at 180 °C for 25 min were investigated. The loss of moisture and fat in both cheeses were proportional to their initial amounts present; both protein:fat ratio and protein:moisture ratio were higher in half-fat cheese than in full-fat cheese. Various types of protein interactions during melting were measured by dispersing cheeses in different dissociating agents (SDS, EDTA, mercaptoethanol, and urea). Protein interactions which were expressed by dissolving heated cheese in urea appeared to contribute the most; this was followed by those expressed by dissolving in SDS. In interaction with temperature, dissociating agents appeared to have the greatest effect on the undissociated proteins still present. The protein–protein interactions during melting of cheeses, which form the hard surface skin in reduced-fat cheeses, were shown to involve disulfide bonds and hydrophobic interactions and to some extent ionic bonds with calcium.